Fin-type field effect transistors (“FinFETs”) have become increasingly widespread in advanced manufacturing of ICs because FinFETs offer better electrostatic control over the behavior in the channel than planar field-effect-transistors (FETs). A FinFET generally includes source, drain, and gate regions, wherein the gate region is placed between the source and drain regions and controls the current through a channel region (often shaped as a semiconductor fin) between the source and drain regions. FinFETs are generally formed by creating a number of semiconductor fins on a substrate and placing a gate conductor perpendicularly across the fins. By applying an appropriate voltage to the gate electrode, the channel region becomes conductive and current is allowed to flow from the source region to the drain region. Contacts to each of the source, drain, and gate regions through a dielectric layer provide electrical connection with other integrated circuit components (e.g., transistors, capacitors etc.) or metal layers that are formed on a substrate.
To improve the operating speed of FinFETs and to increase the density of FinFETs on an integrated circuit, device designers have greatly reduced the physical size of FinFETs over the years. There are a number of challenges that arise as feature sizes of FinFETs and integrated circuits get smaller.
For example, in FinFETs, a wrap-around contact (WAC) may be formed over most of the outer surface of source/drain regions in order to reduce contact resistance in the FinFET. To ensure that the WAC is formed around most of the outer surface of source/drain regions, a large contact area is typically etched over the source/drain regions such that all outer surfaces of the source/drain regions are exposed. However, the large contact area limits the device scaling, because the spacing between individual devices is limited by the width of the contact area used to form the WAC. Therefore, as FinFETs continue to scale downward in size, it is desirable to optimize the WAC area over the outer surface of source/drain regions.